This invention relates to a fuel delivery system suitable for a gas turbine engine. The invention uses a cavitating venturi to deliver and meter the fuel to the turbine and simplify the system.
Fuel delivery systems for gas turbine engines are expensive and include numerous complex parts. The fuel delivery system is controlled by scheduling fuel flow as a function of an electronic engine controller (EEC) command based upon a fuel metering valve position and a linear variable displacement transducer used to provide feedback.
Conventional fuel controls use a precision-matched fuel metering valve, which is displaced along its axis by servo pressure. A linear variable displacement transducer is used to determine the exact position of the valve, which, in turn, implies its full capacity at that specific displacement. The fuel metering valve does not close off so that it is leak tight, thereby requiring that another minimum pressure and shut-off valve be used downstream of the fuel metering valve. The pressure drop across the fuel metering valve must be kept constant so a pressure regulating valve is used in parallel with the fuel metering valve. A reduced servo pressure is maintained by a servo pressure regulator.
The matched valves, linear variable displacement transducers, and other components, are all quite complicated and prone to high rates of rejection due to their complexity. These components also have high costs and long lead times. Therefore, what is needed is a pressure-based fuel metering unit that eliminates the fuel metering valve, linear variable displacement transducer, and other complicated and expensive components.